Method of providing a silicon film having a roughened outer surface

Abstract

A method of providing a silicon film having a roughened outer surface atop a semiconductor wafer comprises: a) placing a semiconductor wafer into a plasma enhanced RF powered chemical vapor deposition reactor; and b) plasma enhanced chemical vapor depositing a layer of silicon over the wafer surface by providing quantities of a silicon source gas, a carrier gas, and TiCl 4 to the reactor, the atomic ratio of the quantities of silicon source gas and TiCl 4 being greater than or equal to 4 at the wafer surface; and by maintaining the reactor at a selected RF power, pressure and temperature; the RF power being supplied at a frequency of at least 5 MHz and preferably at least 10 MHz, the quantities of silicon source gas, RF power, temperature and pressure being effective to produce a predominately silicon film having an outer surface, the quantity of TiCl 4 being effective to induce roughness into the outer silicon surface as compared to an outer silicon surface prepared under identical conditions but for introduction of TiCl 4 but ineffective to produce a predominately titanium silicide film.

We claim: 
     
       1. A method of providing a silicon film having a roughened outer surface atop a semiconductor wafer, the method comprising the following steps: placing the semiconductor wafer having a surface into a plasma enhanced RF powered chemical vapor deposition reactor; and   plasma enhanced chemical vapor depositing a layer of silicon over the wafer surface by providing quantities of a silicon source gas, a carrier gas, and TiCl 4  to the reactor, an atomic ratio of the quantities of the silicon source gas and the TiCl 4  being greater than or equal to 4 at the wafer surface; and by maintaining the reactor at an RF power, a pressure and a temperature; the RF power being supplied at a frequency of at least 5 MHz, the quantities of the silicon source gas, the RF power, the temperature and the pressure being effective to produce a predominately silicon film having the outer surface, the quantity of the TiCl 4  being ineffective to produce a predominately titanium silicide film.   
     
     
       2. The method of providing a silicon film having a roughened outer surface of claim 1 wherein the RF power is supplied at a frequency of at least 10 MHz. 
     
     
       3. The method of providing a silicon film having a roughened outer surface of claim 1 wherein the atomic ratio of the quantities of the silicon source gas and the TiCl 4  is greater than or equal to 10. 
     
     
       4. The method of providing a silicon film having a roughened outer surface of claim 1 wherein the atomic ratio of the quantities of the silicon source gas and the TiCl 4  is greater than or equal to 50. 
     
     
       5. The method of providing a silicon film having a roughened outer surface of claim 1 wherein the atomic ratio of the quantities of the silicon source gas and the TiCl 4  is greater than or equal to 100. 
     
     
       6. The method of providing a silicon film having a roughened outer surface of claim 1 wherein the RF power, the pressure and the temperature are selected to deposit a polycrystalline silicon film. 
     
     
       7. The method of providing a silicon film having a roughened outer surface of claim 1 further comprising depositing a 50 Angstrom to 1500 Angstrom thin film atop the wafer over the outer silicon surface to impart permanency to its contour. 
     
     
       8. The method of providing a silicon film having a roughened outer surface of claim 1 wherein the silicon source gas comprises SiH 4 . 
     
     
       9. A method of providing a polysilicon film having a roughened outer surface atop a semiconductor wafer, the method comprising the following steps: placing the semiconductor wafer having a surface into a plasma enhanced RF powered chemical vapor deposition reactor;   plasma enhanced chemical vapor depositing a layer of amorphous silicon over the wafer surface by providing quantities of a silicon source gas, a carrier gas, and TiCl 4  to the reactor, an atomic ratio of the quantities of the silicon source gas and the TiCl 4  being greater than or equal to 4 at the wafer surface; and by maintaining the reactor at an RF power, a pressure and a temperature; the RF power being supplied at a frequency of at least 5 MHz, the quantities of the silicon source gas, the RF power, the temperature and the pressure being effective to produce a predominately amorphous silicon film having the outer surface, the quantity of the TiCl 4  being ineffective to produce a predominately titanium silicide film; and   annealing the wafer to render the amorphous silicon polycrystalline.   
     
     
       10. The method of providing a polysilicon film having a roughened outer surface of claim 9 wherein the RF power is supplied at a frequency of at least 10 MHz. 
     
     
       11. The method of providing a polysilicon film having a roughened outer surface of claim 9 wherein the atomic ratio of the quantities of the silicon source gas and the TiCl 4  is greater than or equal to 10. 
     
     
       12. The method of providing a polysilicon film having a roughened outer surface of claim 9 wherein the atomic ratio of the quantities of the silicon source gas and the TiCl 4  is greater than or equal to 50. 
     
     
       13. The method of providing a polysilicon film having a roughened outer surface of claim 9 wherein the atomic ratio of the quantities of the silicon source gas and the TiCl 4  is greater than or equal to 100. 
     
     
       14. The method of providing a polysilicon film having a roughened outer surface of claim 9 further comprising depositing a 50 Angstrom to 1500 Angstrom thin film atop the wafer over the outer silicon surface to impart permanency to its contour. 
     
     
       15. The method of providing a silicon film having a roughened outer surface of claim 9 wherein the silicon source gas comprises SiH 4 . 
     
     
       16. A method of providing a silicon film having a roughened outer surface atop a semiconductor wafer, the method comprising the following sequential steps: placing the semiconductor wafer having a surface into a plasma enhanced RF powered chemical vapor deposition reactor;   plasma enhanced chemical vapor depositing a first layer of silicon over the wafer surface by feeding quantities of a silicon source gas, a carrier gas, and TiCl 4  to the reactor, an atomic ratio of the quantities of the silicon source gas and the TiCl 4  being greater than or equal to 4 at the wafer surface; and by maintaining the reactor at an RF power, a pressure and a temperature; the RF power being supplied at a frequency of at least 5 MHz, the quantities of the silicon source gas, the RF power, the temperature and the pressure being effective to produce a first predominately silicon film having a first outer surface, the quantity of the TiCl 4  being effective to induce roughness into the first outer silicon surface as compared to an outer silicon surface prepared under identical conditions but for introduction of the TiCl 4  but the quantity of the TiCl 4  being ineffective to produce a predominately titanium silicide film; and   ceasing to feed the TiCl 4  to the reactor while continuing to the silicon source gas to the reactor, and maintaining the RF power, the pressure and the temperature at quantities effective to deposit a second layer of silicon atop the first outer surface of the first layer of silicon, the second layer of silicon having a second outer surface, the first outer surface at least in part inducing roughness into the second outer surface.   
     
     
       17. The method of providing a silicon film having a roughened outer surface of claim 16 wherein the RF power is supplied at a frequency of at least 10 MHz. 
     
     
       18. The method of providing a silicon film having a roughened outer surface of claim 16 wherein the atomic ratio of the quantities of the silicon source gas and the TiCl 4  is greater than or equal to 10. 
     
     
       19. The method of providing a silicon film having a roughened outer surface of claim 16 wherein the atomic ratio of the quantities of the silicon source gas and the TiCl 4  is greater than or equal to 50. 
     
     
       20. The method of providing a silicon film having a roughened outer surface of claim 16 wherein the atomic ratio of the quantities of the silicon source gas and the TiCl 4  is greater than or equal to 100. 
     
     
       21. The method of providing a silicon film having a roughened outer surface of claim 16 wherein the RF power, the pressure and the temperature are selected to deposit the first layer of silicon which is polycrystalline. 
     
     
       22. The method of providing a silicon film having a roughened outer surface of claim 16 wherein the RF power, the pressure and the temperature are selected to deposit polycrystalline first and second layers of silicon. 
     
     
       23. The method of providing a silicon film having a roughened outer surface of claim 16 further comprising depositing a 50 Angstrom to 1500 Angstrom thin film atop the wafer over the second roughened outer silicon surface to impart permanency to the roughness. 
     
     
       24. The method of providing a silicon film having a roughened outer surface of claim 16 wherein the silicon source gas comprises SiH 4 . 
     
     
       25. A method of providing a polysilicon film having a roughened outer surface atop a semiconductor wafer, the method comprising the following sequential steps: placing the semiconductor wafer having a surface into a plasma enhanced RF powered chemical vapor deposition reactor;   plasma enhanced chemical vapor depositing a first layer of amorphous silicon over the wafer surface by feeding quantities of a silicon source gas, a carrier gas, and TiCl 4  to the reactor, an atomic ratio of the quantities of the silicon source gas and the TiCl 4  being greater than or equal to 4 at the wafer surface; and by maintaining the reactor at an RF power, a pressure and a temperature; the RF power being supplied at a frequency of at least 5 MHz, the quantities of the silicon source gas, the RF power, the temperature and the pressure being effective to produce a first predominately amorphous silicon film having a first outer surface, the quantity of the TiCl 4  being effective to induce roughness into the first outer amorphous silicon surface as compared to an outer amorphous silicon surface prepared under identical conditions but for introduction of the TiCl 4  but the quantity of the TiCl 4  being ineffective to produce a predominately titanium silicide film;   ceasing to feed the TiCl 4  to the reactor while continuing to feed the silicon source gas to the reactor, and maintaining the RF power, the pressure and the temperature at quantities effective to deposit a second layer of silicon atop the first outer surface of the first layer of silicon, the second layer of silicon having a second outer surface, the first amorphous outer surface at least in part inducing roughness into the second outer surface; and   annealing the wafer to render the first amorphous film polycrystalline.   
     
     
       26. The method of providing a polysilicon film having a roughened outer surface of claim 25 wherein the RF power is supplied at a frequency of at least 10 MHz. 
     
     
       27. The method of providing a polysilicon film having a roughened outer surface of claim 25 wherein the atomic ratio of the quantities of the silicon source gas and the TiCl 4  is greater than or equal to 10. 
     
     
       28. The method of providing a polysilicon film having a roughened outer surface of claim 25 wherein the atomic ratio of the quantities of the silicon source gas and the TiCl 4  is greater than or equal to 50. 
     
     
       29. The method of providing a polysilicon film having a roughened outer surface of claim 25 wherein the atomic ratio of the quantities of the silicon source gas and the TiCl 4  is greater than or equal to 100. 
     
     
       30. The method of providing a silicon film having a roughened outer surface of claim 25 wherein the RF power, the pressure and the temperature are selected to deposit a first layer of silicon which is amorphous, the step of annealing comprising annealing the wafer to render the first and second films polycrystalline. 
     
     
       31. The method of providing a polysilicon film having a roughened outer surface of claim 25 further comprising depositing a 50 Angstrom to 1500 Angstrom thin film atop the wafer over the roughened outer silicon surface to impart permanency to the roughness.